Building up pressure in value cover

[455bird]

i have a 08 kx450f that i checked the values on last night, they where ok put the bike back together and started it and the value cover was leaking oil. i went to pull off and found that its building up pressure when the bike is running. what am i looking at a value leaking or what? bike is not smoking it run good

[don46]

Was it leaking before you checked the valves? if not then for sure you missed something. A leaking valve will generally not cause crankcase pressure, bad rings could. is your crankcase vent pinched? I've seen that happen. where is it leaking oil? there is an oring under one of the cam caps that if missing will cause a leak out the small hole in the side of the head, this is from the spark plug area. there is always some pressure as it warms up.